The present disclosure relates to a fuel pump assembly. Moreover, the present disclosure relates to each one of an internal combustion engine, a vehicle and a method for pressurizing fuel using a fuel pump assembly.
Fuel pump assemblies for supplying high-pressure fuel to fuel injectors are known. Generally, such a system comprises a low pressure fuel system feeding fuel to a pumping chamber co-operating with a plunger for further pressurizing the fuel.
One potential problem with such a fuel pump assembly is that fuel leakage may occur, for instance between the plunger and the component(s) accommodating the plunger. In order to handle such a possible leakage, WO 2012/171593 A1 proposes the use of a drain line for draining at least fuel vapour from an interior of a pump block.
Although the solution as proposed in WO 2012/171593 A1 is appropriate for many applications, there may still be a need for improving fuel pump assemblies for pressurizing fuel, such as DME.
It is desirable to provide a fuel pump assembly in which fuel leakage can be handled in an appropriate manner.
As such, the present disclosure relates to a fuel pump assembly for pressurizing fuel. The fuel preferably comprises dimethyl ether (DME). The fuel pump assembly comprises a plunger assembly and a pump block defining a pumping chamber and a plunger assembly cavity in communication with the pumping chamber. The plunger assembly is movable at least partially in the plunger assembly cavity towards and away from the pumping chamber. The fuel pump assembly comprises a metering valve and a suction channel located between the metering valve and the pumping chamber in an intended direction of flow of the fuel. The fuel pump assembly comprises a leakage return conduit, with a first leakage return conduit opening in fluid communication with the plunger assembly cavity, adapted to return fuel that has leaked from the pumping chamber.
According to the present disclosure, the leakage return conduit comprises a second leakage return conduit opening located in the suction channel.
The suction channel generally has few components vulnerable to deposits generated by the fuel. Also, conditions that generally exist in the suction channel suppress formation of fuel deposits in the parts of it that may impact the performance of the fuel pump assembly. As such, a fuel pump assembly as has been presented hereinabove, in which the leakage return conduit is in fluid communication with the suction channel, implies an appropriately low risk for deposits of returned leaked fuel in the fuel supply system as compared to prior art systems wherein leaked fuel is instead recirculated to portions of a fuel supply system that have a lower pressure, e.g. back to a fuel tank.
Optionally, the leakage return conduit provides a direct fluid communication between the plunger assembly cavity and the suction channel. As a non-limiting example, the leakage return conduit may be constantly open. For instance, the leakage return conduit may be free from flow regulating means such as valves.
Optionally, the first leakage return conduit opening is located in the plunger assembly cavity.
Optionally, the plunger assembly cavity comprises a leakage chamber at least partially surrounding the plunger assembly. The first leakage return conduit opening is located in the leakage chamber.
Optionally, the fuel pump assembly comprises a first sealing means for preventing fuel from escaping from the pumping chamber along the plunger assembly.
The first sealing means implies an appropriately low rate of leakage past the plunger.
Optionally, the first sealing means is obtained by means of a clearance between the plunger assembly and a portion of the pump block, preferably a metal portion of the pump block. The clearance is preferably within the range of 0.1 to 10 micrometres, more preferred within the range of 0.5 to 5 micrometres.
The above clearance implies a preferred implementation for achieving the first sealing means.
Optionally, the first leakage return conduit opening is located downstream of the first sealing means.
Optionally, the fuel pump assembly comprises a second sealing means for preventing fuel that has passed the first sealing means from passing further along the plunger assembly. The leakage return conduit opening is located between the pumping chamber and the second sealing means.
The second sealing means implies an increased possibility to transport leaked fuel via the leakage return conduit.
Optionally, the second sealing means is obtained by means of a clearance between the plunger assembly and a portion of the pump block, preferably a metal portion of the pump block, the clearance preferably being within the range of 0.1 to 10 micrometres, more preferred within the range of 0.5 to 5 micrometres.
The above clearance implies a preferred implementation for achieving the second sealing means.
Optionally, the second sealing means comprises an elastomer and/or a plastics material with or without an energizer. Preferably, the second sealing means comprises an elastomer and/or a plastics material which is compatible with DME. As a non-limiting example, the second sealing means may comprise a perfluoroelastomer (FFKM) and/or a polytetrafluoroethylene (PTFE).
Optionally, the fuel pump assembly further comprises a bleed valve adapted to selectively provide a fluid communication, preferably via a return channel, between the suction channel and a source of fuel.
Optionally, the suction channel comprises a discharge port adapted to discharge fuel to the pumping chamber. The bleed valve and the metering valve are located on opposite sides of the discharge port.
Optionally, the suction channel comprises a discharge port adapted to discharge fuel to the pumping chamber. The metering valve and the discharge port are located on opposite sides of the bleed valve.
Optionally, when measured along an intended direction of flow in the suction channel, the bleed valve is located a first distance from the metering valve and the discharge port is located a second distance from the bleed valve. The second distance is smaller than the first distance.
Optionally, the fuel pump assembly comprises an inlet valve, preferably a spring-less inlet valve such as a disc valve, positioned between the suction channel and the pumping chamber, adapted to control the flow of fuel into the pumping chamber.
Optionally, the pumping chamber assumes a minimum volume when the plunger assembly is at a top position and the pumping chamber assumes a maximum volume when the plunger assembly is at a bottom position. The maximum volume is within the range of 10 to 30, preferably within the range of 12 to 15, times the minimum volume.
Optionally, the leakage return conduit comprises a leakage return cavity in the pump block, preferably the leakage return cavity having a circumferential extension in a circumferential direction and the leakage return cavity at least partially circumscribes the plunger assembly cavity and/or the pumping chamber in the circumferential direction.
The leakage return cavity according to the above implies that leaked fuel, upon its possible evaporation in the leakage return cavity, would impart more of the cooling effect due to evaporation onto the parts of the pumping system that contact the fuel and, consequently, suppress evaporation of fuel in the pumping chamber during the filling stroke of the plunger assembly. This would help improve the volumetric efficiency of the pump.
Optionally, the plunger assembly comprises a plunger and a tappet. The plunger assembly cavity comprises a plunger cavity portion, adapted to accommodate at least a portion of the plunger, and a tappet cavity portion, adapted to accommodate at least a portion of the tappet, wherein the fuel pump assembly comprises a drain conduit for draining fluid that has leaked past a portion of the plunger assembly, for instance past at least a portion of the plunger. The drain conduit comprises a drain conduit opening located in the tappet cavity portion.
Optionally, the plunger assembly comprises a force-transferring bearing for transferring forces from a camshaft to the plunger assembly.
Optionally, the fuel pump assembly comprises a feeding fuel pump assembly adapted to feed fuel to the pumping chamber.
Optionally, the feeding fuel pump assembly is located upstream of the metering valve in an intended direction of flow of the fuel.
A second aspect of the present disclosure relates to an internal combustion engine comprising a fuel pump assembly according to the first aspect of the present disclosure.
A third aspect of the present disclosure relates to a vehicle, preferably a heavy-duty vehicle, comprising a fuel pump assembly according to the first aspect of the present disclosure and/or an internal combustion engine according to the second aspect of the present disclosure.
A fourth aspect of the present disclosure relates to a method for pressurizing fuel using a fuel pump assembly. The fuel preferably comprises dimethyl ether (DME). The fuel pump assembly comprises a plunger assembly and a pump block defining a pumping chamber and a plunger assembly cavity. The fuel pump assembly comprises a metering valve and a suction channel located between the metering valve and the pumping chamber in an intended direction of flow of the fuel. The method comprises:
pressurizing the fuel in the pumping chamber by moving the plunger assembly at least partially in the plunger assembly cavity, and
guiding leaked fuel, having leaked from the pumping chamber to the plunger assembly cavity, directly back to the suction channel.
A fifth aspect of the present disclosure relates to a fuel pump assembly for pressurizing fuel, the fuel preferably comprising dimethyl ether (DME). The fuel pump assembly comprising a plunger assembly and a pump block. The pump block defines a pumping chamber and a plunger assembly cavity in fluid communication with the pumping chamber. The plunger assembly is movable at least partially in the plunger assembly cavity towards and away from the pumping chamber. The plunger assembly comprises a plunger and a tappet wherein the cross-sectional area of the tappet is larger than the cross-sectional area of the plunger. The plunger assembly cavity comprises a tappet cavity portion, adapted to accommodate at least a portion of the tappet.
According to the fifth aspect of the present disclosure, the fuel pump assembly comprises a drain conduit with a drain conduit opening located in the tappet cavity portion.
A fuel pump assembly according to the fifth aspect of the present disclosure implies that fluid that has leaked passed the plunger may be handled in an efficient manner. Since the cross-sectional area of the tappet is larger than the cross-sectional area of the plunger, fluid that has leaked past the plunger enters a space, the cross-sectional area of which is larger than the cross-sectional area of the plunger. This in turn implies that leaked fluid may enter the drain conduit, even if the fluid has not leaked past a portion of the circumference of the plunger that is close to the drain conduit opening.
Optionally, the cross-sectional area of the tappet may be at least 2 times greater, preferably at least 5 times greater, more preferred at least 8 times greater, than the cross-sectional area of the plunger.
Optionally, the fuel pump assembly comprises a plunger cavity portion, adapted to accommodate at least a portion of the plunger, and a leakage return conduit with a first leakage return conduit opening located in the plunger cavity portion.
Optionally, the fuel pump assembly comprises a metering valve and a suction channel located between the metering valve and the pumping chamber in an intended direction of flow of the fuel. The leakage return conduit comprises a second leakage return conduit opening located in the suction channel.
Optionally, the leakage return conduit comprises a leakage return cavity in the pump block. Preferably the leakage return cavity has a circumferential extension in a circumferential direction and the leakage return cavity at least partially circumscribes a portion of the plunger assembly cavity and/or a portion of the pumping chamber in the circumferential direction.
Optionally, the plunger cavity portion comprises a leakage chamber at least partially surrounding the plunger. The leakage return conduit opening is located in the leakage chamber.
Optionally, the fuel pump assembly comprises a first sealing means for preventing fuel from escaping from the pumping chamber along the plunger assembly. The first sealing means is located between the pumping chamber and the leakage return conduit opening.
Optionally, the first sealing means is obtained by means of a clearance between the plunger and a portion of the pump block, preferably a metal portion of the pump block. The clearance preferably is within the range of 0.1 to 10 micrometres, more preferred within the range of 0.5 to 5 micrometres.
Optionally, the fuel pump assembly comprises a second sealing means for preventing fuel from escaping from the pumping chamber along the plunger assembly. The leakage return conduit opening is located between the pumping chamber and the second sealing means.
Optionally, the second sealing means is obtained by means of a clearance between the plunger and a portion of the pump block, preferably a metal portion of the pump block. The clearance preferably is within the range of 0.1 to 10 micrometres, more preferred within the range of 0.5 to 5 micrometres.
Optionally, the plunger assembly and the pump block are arranged such that a tappet seal is obtained for preventing fuel from passing between a portion of the tappet and the pump block.
By virtue of the tappet seal, prevention or at least a penetration reduction of leakage past the tappet, into e.g. a camshaft space, may be obtained in a simple and inexpensive manner. Limiting the penetration of leakage into the camshaft space may simplify collection and removal of leakage from the pump and may reduce unwanted interaction of leakage with other liquids, e.g. lubrication oil which is normally present in the camshaft space.
Optionally, the tappet seal is obtained by means of a clearance between the tappet and a portion of the pump block, preferably a metal portion of the pump block. The clearance preferably is within the range of 5 to 100 micrometres, more preferred within the range of 20 to 40 micrometres.
Optionally, the fuel pump assembly comprises an inlet valve, preferably a spring-less inlet valve such as a disc valve, positioned between the suction channel and the pumping chamber, adapted to control the flow of fuel into the pumping chamber.
Optionally, the pumping chamber assumes a minimum volume when the plunger assembly is at a top position and the pumping chamber assumes a maximum volume when the plunger assembly is at a bottom position. The maximum volume is within the range of 10 to 30, preferably within the range of 12 to 15, times the minimum volume.
Optionally, the plunger assembly comprises a force-transferring bearing for transferring forces from a camshaft to the tappet.
Optionally, the fuel pump assembly comprises a feeding fuel pump assembly adapted to feed fuel to the pumping chamber.
Optionally, the feeding fuel pump assembly is located upstream of the metering valve in an intended direction of flow of the fuel.
Optionally, the fuel pump assembly further comprises a bleed valve adapted to selectively provide a fluid communication, preferably via a return channel, between the suction channel and a source of fuel.
Optionally, the suction channel comprises a discharge port adapted to discharge fuel to the pumping chamber. The bleed valve and the metering valve are located on opposite sides of the discharge port.
Optionally, the suction channel comprises a discharge port adapted to discharge fuel to the pumping chamber. The metering valve and the discharge port are located on opposite sides of the bleed valve.
Optionally, when measured along an intended direction of flow in the suction channel, the bleed valve is located a first distance from the metering valve and the discharge port is located a second distance from the bleed valve. The second distance is smaller than the first distance.
Optionally, the plunger assembly is adapted to be driven by a driving member which is rotatably mounted in a housing which is connected to the pump block. The fuel pump assembly further comprises a lube oil supply line connected to the housing.
Optionally, the fuel pump assembly further comprises a lube oil reservoir outside the housing. The lube oil supply line provides a fluid communication between the lube oil reservoir and the housing. The fuel pump assembly further comprises a lube oil separator in fluid communication with the lube oil reservoir. The drain conduit is adapted to be in fluid communication with the lube oil separator.
Optionally, the drain conduit is connected to a valve, such as a solenoid valve, which in turn is connected to the lube oil separator. The valve is adapted to control the fluid communication between the drain conduit and the lube oil separator.
Optionally, the fuel pump assembly further comprises a second drain conduit. The second drain conduit is in fluid communication with the housing.
Optionally, the second drain conduit is in fluid communication with the valve.
Optionally, the lube oil supply line comprises a lube oil supply valve, preferably a check valve.
A sixth aspect of the present disclosure relates to an internal combustion engine comprising a fuel pump assembly according to the fifth aspect of the present disclosure.
A seventh aspect of the present disclosure relates to a vehicle, preferably a heavy-duty vehicle, comprising a fuel pump assembly in accordance with the fifth aspect of the present disclosure and/or an internal combustion engine according to the sixth aspect of the present disclosure.
It should be noted that the appended drawings are not necessarily drawn to scale and that the dimensions of some features of the present invention may have been exaggerated for the sake of clarity.